Ireland
I Got Irish Citizenship Through Foreign Birth Registration. Can My Children Get It Too?
Short answer: it depends on whether your children were born before or after you were entered on the Foreign Births Register.
Born after you registered
If your children were born after your entry on the Foreign Births Register, they're eligible to apply for entry on the register too. Source: ireland.ie, FBR FAQ
Born before you registered
If your children were born before you were registered, they aren't eligible to apply, because you weren't an Irish citizen at the time of their birth. Source: ireland.ie, FBR FAQ Citizenship through FBR is effective from the date of registration, not from your date of birth. Source: Citizens Information
Citizens Information sums it up this way: a great-grandchild of someone born on the island of Ireland is entitled to Irish citizenship through FBR only if their parent had registered by the time of their birth. Source: Citizens Information
Is there any other route?
Unless a parent or an Irish-born grandparent was an Irish citizen at the time of your birth, there's no automatic right to Irish citizenship through more distant ancestors. Source: Citizens Information Ireland's Minister can grant citizenship based on Irish associations (being related by blood or adoption to an Irish citizen), but this is discretionary. Source: Citizens Information
If you're expecting a baby
If you're an expectant parent applying to be entered on the register, Ireland says to mark this clearly on your application. Source: ireland.ie
Siblings can share documents
Brothers and sisters applying through the same parent or grandparent can use the same set of supporting documents. Put the separate application forms in one envelope with a letter saying which documents apply to both. This only works if you live in the same country. Source: ireland.ie, FBR FAQ
Documents for your child
Whether your child applies as an adult or a minor, the documents for you, the Irish citizen parent, include your original Foreign Birth Registration certificate. Source: ireland.ie The FBR fee is €278 for over-18s and €153 for under-18s, including return postage. Source: ireland.ie